Re: [PATCH] srcutiny: Add lockdep and early-boot checks to synchronize_srcu_atomic()

[Paul E. McKenney]

On Fri, Sep 11, 2026 at 10:18:04PM +0100, Bradley Morgan wrote:
> On 11 September 2026 17:09:13 BST, Kunwu Chan <kunwu.chan@xxxxxxxxx> wrote:
> >Add the RCU_LOCKDEP_WARN and early-boot check that the Tree version
> >gained, srcu_lock_sync() was already present.
> >
> >Suggested-by: Zqiang <qiang.zhang@xxxxxxxxx>
> 
> Ok.
> 
> Reviewed-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>

Applied, thank you!

> >Signed-off-by: Kunwu Chan <kunwu.chan@xxxxxxxxx>
> >---
> > kernel/rcu/srcutiny.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> >diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
> >index 99f8bfd98b04..76411562366f 100644
> >--- a/kernel/rcu/srcutiny.c
> >+++ b/kernel/rcu/srcutiny.c
> >@@ -361,6 +361,12 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
> > 
> > 	srcu_lock_sync(&ssp->dep_map);
> > 
> >+	RCU_LOCKDEP_WARN(lockdep_is_held(ssp),
> >+			 "Illegal synchronize_srcu_atomic() in same-type SRCU read-side critical section");
> >+
> >+	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
> >+		return;
> >+
> 
> Wow!

If you think that this one is fun, take a look at the implementation of
synchronize_rcu() in kernel/rcu/tiny.c.  ;-)

							Thanx, Paul

> > 	if (IS_ENABLED(CONFIG_PREEMPTION))
> > 		synchronize_rcu(); // Needed for RCU Tasks Trace to imply RCU grace period.
> > 				   // And in Tiny RCU, it is near zero cost and doesn't block.
> >
> 
> --- Thanks!
> https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@xxxxxxxxx/